Rice heading time (flowering time) is mainly determined by photoperiod sensitivity that depends on day length and other factors (basal vegetative growth or temperature sensitivity). Genetic analysis of heading time has been performed for some time, and to date, heading time-associated genes such as Se1 locus (chromosome 6), E1 locus (chromosome 7), E2 locus (unknown), E3 locus (chromosome 3), or Ef1 locus (chromosome 10) (Kinoshita, Rice Genetics Newsletter 15: 13-74, 1998; Nishida et al., Ann. Bot. 88: 527-536, 2001) have been discovered using mutations and variations inherent to rice cultivars. Recently, the use of DNA markers in rice genetic analyses has advanced the genetic analysis of characteristics such as heading time that exhibits complex inheritance (quantitative traits) (Yano et al., Plant Physiol. 127: 1425-1429, 2001). Genes associated with rice photoperiod sensitivity have been isolated based on this work (Yano et al., Plant Cell 12: 2473-2484, 2000; Takahashi et al., PNAS 98: 7922-7927, 2001; Kojima et al., Plant Cell Physiol. 43: 1096-1105, 2002; Yano, Curr. Opin. Plant Biol. 4: 130-135, 2001). Attempts to use these isolated rice-heading-time-associated genes to elucidate genetic control mechanisms are also progressing (Izawa et al., Gene Dev. 16: 2006-2020, 2002; Hayama et al., Nature 422: 719-722, 2003). On the other hand, many cases of isolation of genes associated with plant flowering have been reported in Arabidopsis thaliana (Simpson, G. G. and Dean, C., Science 296: 285-289 (2002); Mouradov, A. et al., Plant Cell (Suppl.) 14: S111-130 (2002)). Furthermore, methods for controlling flowering time in Arabidopsis thaliana (a plant) using these genes have been proposed (Published Japanese Translation of International Publication Nos.: 2002-511270; 2002-532069; 2002-537768; 2000-512845; Hei 11-512289; Hei 11-506001; and Hei 10-508481). At the same time, a method for using rice genes to alter the flowering time of Arabidopsis thaliana (a plant) has also been suggested (Published Japanese Translation of International Publication No. 2002-335970). However, a great number of the genes associated with rice heading time remain to be isolated.